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_ <br /> FY , <br /> A--3 <br /> ~ If hydrocarbon odors or signs of hydrocarbon are detected in a <br /> soil sample, selected soil samples will be analyzed for benzene, <br /> toluene, xylene (BTX) (U.S. Environmental Protection Agency (LPA) <br /> Method 8020) , total petroleum fuel hydrocarbons (modified EPA 8015) , <br /> and total lead. The samples will be delivered to BC's analytical <br /> laboratory in Emeryville within 48 hours of collection. <br /> Groundwater Monitoring Wells <br /> During monitoring well installation, the following procedures <br /> will be used. These methods will ensuro the proper identification of <br /> ' groundwater quality beneath the site. <br /> Groundwater Monitoring well installation. Three groundwater <br /> monitoring wells will be installed in the boreholes shown on <br /> Figure 1. A total of three groundwater monitoring wells is required <br /> ' W to determine groundwater gradient and flow direction. <br /> The wells will be completed with 2-.inch-diameter polyvinyl <br /> chloride (PVC) flush-threaded casing and will be screened with <br /> 0.020--inch slotted casing from 10 feet below the groundwater surface <br /> to 5 feet above the groundwater surface. Blank casing will extend <br /> from the top of the perforated section to ground surface. The actual <br /> depths of the boreholes and screened intervals of the wells will <br /> depend on conditions encountered during drilling. <br /> w� The wells will be packed with No. 20/40 sand from the bottom of <br /> the screen to approximately 2 feet above the top of the screen. A <br /> 2-foot seal of bentonite pellets will be placed on the top of the <br /> - sand pack. The wells will be grouted with bentonite-cement slurry or <br /> neat cement from the top of the bentonite seal to the surface. The <br /> -- wells will be completed below grade, fitted withtap and bottom PVC <br /> caps, and have locking covers installed. Typical well construction <br /> is illustrated on Figure 2. <br /> The monitoring wells will not be completed opposite significant <br /> clay zones nor will monitoring wells penetrate significant clay zones <br /> that might allow for downward migration of contamination <br /> aquifers. into lower <br /> I Well Development and Groundwater Samples. Each well installed <br /> will be developed by surging and <br /> bailing until clean, sediment-free <br /> water is produced from the well. The length of development time <br /> will vary depending upon field conditions. Water produced during <br /> . r development and sampling will be contained on site. ARCO will be <br /> responsible for the disposal of water and product collected. Prior <br /> to and following development, the thicknessoffree <br /> _-prod uct, i€_any-,_- <br /> - <br /> Y <br />